Vehicle drive track stiffener

ABSTRACT

An endless molded rubber drive track or belt is disclosed having two rows of longitudinally spaced openings for engagement with the teeth of a pair of drive sprocket wheels. A plurality of stiffeners formed from unidirectional fiber glass are carried within the belt between the inner and outer surfaces thereof. Each stiffener extends substantially the full transverse width of the belt between adjacent openings to impart transverse rigidity to the belt.

United States Patent PATENTEU Aus l o |91:

N dauw PATENTEU Aulolsm 3,598,454

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'IIIIIIIIIIIIIIII INVENTOR y 'VV/UAM R. R/CHARos -FIG.' I

MERCHANT Gouw A T TOR/VE Ys VEHICLE DRIVE TRACK STIFFENER BACKGROUND OFTHE INVENTION l. Field of the Invention This invention relates generallyto the field of endless drive belt construction, but more specificallyrelates to the construction for a flexible drive track for a snowmobile,the drive track having a plurality of transverse fiber glass stiffenersincorporated as a part thereof.

2. Description of the Prior Art The typical snowmobile utilizes anendless drive track or belt to carry a major portion of the vehicleweight and to drive the vehicle over the ground surface. Then endlessbelt is normally driven from its front end by one or more sprocketwheels and is supported at its opposite end by an idler sprocket system.The intermediate portion of the belt is supported by suitable bogiewheels or other supporting means.

Regardless of how the belt is constructed, it must have certaincharacteristics` The endless belt must be very flexible longitudinallyso that it can freely follow the curvature of the drive and idlersprocket wheels. At the same time, however, the belt should be veryrigid in a transverse direction so as to provide firm support for thevehicle. In any vehicle of this type, the drive track in effect laysdown a temporary road over which the vehicle passes. lf the greatestefficiency and speed of operation is to be obtained, the track must beas flat and rigid as possible during the time it is in contact with theground. Since the belt cannot be made rigid longitudinally, it must bemade relatively rigid in a transverse direction. lf the belt were notmade rigid in at least one direction, it would tend to bend upwardlyaround the bogie wheels so that only a small portion of the belt wouldstay in contact with the ground. Since the reason for using a belt is todistribute the weight of the vehicle over as wide an area as possible, abelt having no transverse rigidity at all would not function properly.By making the belt relatively rigid in a transverse direction, the loadis more evenly distributed over the entire surface of the belt, thismaking the vehicle more stable and permitting it to operate efficientlyover a wide variety of supporting surfaces.

Prior art snowmobiles have incorporated various devices for increasingthe transverse rigidity of the drive belt. Perhaps the most commonlyused type of prior art drive belt has been the flexible rubber or fabricbelt having metal cleats riveted to the ground engaging surface of thebelt. The cleats normally extend the full width of the belt and not onlyprovide rigidity but also traction for the vehicle. In some cases, thedrive sprocket teeth engage the metal cleats to drive the belt. A priorart belt construction of this general type is shown in the copendingAllan E. Hetteen U.S. patent application, Ser. No. 793,705 filed Jan.24, 1969, now U.S. Pat. No. 3,527,505. While these prior art metalcleats have provided sufficient rigidity, many problems have arisen inconnection with their use. For one thing, they are very heavy and thusadd considerable unnecessary weight to the vehicle. They are expensiveto manufacture and difficult to properly attach to the belt. ln actualpractice, after considerable usage` they tend to break loose from thetrack and in so doing often cause considerable damage to both the trackand the vehicle. Further, the metal cleats tend to be so unflexible thatthey break rather than flex ifa solid object is encountered withconsiderable force.

In order to avoid these problems, attempts have been made in the past toincorporate the metal directly into the belt during manufacture of thebelt. For example, the Bombardier U.S. Pat. No. 2,899,242 that issuedAug. ll, 1959 discloses a molded rubber belt having metal rods formedintegrally therewith. The metal rods are placed in the belt prior to theforming or molding operation so that they are entirely surrounded andsupported by the rubber belt. Thus, in the Bombardier belt, the metalrods do not directly contact the ground and no riveting or other suchattachment method is necessary. In this manner, some of the problemsencountered with the prior art exposed metal cleat were avoided byBombardier.

With the Bombardier structure, however, the problem still exists thatthe metal rods are extremely stiff and do not readily flex in responseto obstacles encountered by the vehicle. Since severe shocks areencountered quite frequently during normal snowmobile usage, it isextremely important that the belt be able to withstand such shockswithout breaking or bending such rods. In the Bombardier structure,there is a tendency for the metal rods to break, bend, or to tear loosefrom the surrounding rubber material during use. The metal rods also addconsiderable undesirable weight to the vehicle,

ln essence, it has been my experience that metal, whether in the formof' cleats or rods, always fatigues and finally breaks. In many cases,the breakage of a single cleat or rod will require replacement of theentire belt.

SUMMARY OF THE INVENTION The present invention overcomes thedisadvantages of the prior art track stiffeners while retaining many oftheir basic advantages. In my invention, a plurality of fiberglassstiffeners are incorporated into the belt during the belt formingoperation. The stiffeners extend transversely of the belt to virtuallythe full width of the belt and are spaced a predetermined distance apartto provide the necessary transverse rigidity. In one embodiment of myinvention, the stiffeners each include a plurality of parallelmonofilament fiberglass threads or fibers embedded in an epoxy resinbinder. These unidirectional fiberglass stiffeners are preformed orextruded as a single unit and are then placed in the belt mold prior tothe molding operation so that they are fully surrounded by the beltmaterial. In another embodiment of my invention, the stiffeners areformed from a group of flat laminations that are cured together to forma solid mass. Each of the laminations comprises a plurality of parallelmonofilament fiberglass threads embedded in a resin binder. In stillanother embodiment, a pair of flat fiberglass strips are securedtogether at their opposite ends and spaced apart intermediate theirends, with the material of the belt extending between the strips as wellas over and under the strips so that a truss structure is formed by eachof the stiffeners.

The fiberglass stiffeners of my invention are normally quite rigid sothat they impart the necessary transverse rigidity to the drive belt.However, the fiberglass stiffeners are also flexible so that in responseto shock, they will flex rather than break. The unidirectionalfiberglass also has a very strong memory such that it will always returnto the same position it was formed in. These stiffeners are also lightin weight, inexpensive to manufacture and easy to incorporate into thebelt during the belt forming operation. Once incorporated into the belt,these stiffeners are virtually unbreakable, thus adding considerablelife to the snowmobile drive belt.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a view in side elevation ofa portion of a snowmobile, including a frame and an endless drive trackmounted thereon; portions thereof shown in section;

FIG. 2 is a plan view ofa portion ofthe ground engaging run of the drivetrack;

FIG. 3 is a view in perspective of a fiberglass stiffener, portionsthereof being broken away;

FIG. 4 is an enlarged sectional view of the drive track and a stiffenertaken along line 4-4 of FIG. 2;

FIG. 5 is an enlarged sectional view of the drive track, the sprocketengaging openings and a plurality of fiberglass stiffeners, taken alongline 5-5 of FIG. 2;

FIG. 6 is an exploded view, in perspective, of a laminated fiberglassstiffener;

FIG. 7 is a greatly enlarged cross-sectional view of a laminatedfiberglass stiffener of the type shown in FIG. 6;

FIG. 8 is a view in perspective of another form of fiberglass stiffenerforming a truss structure;

FIG. 9 is a view similar to that of FIG. 4 but incorporating thestiffener shown in FIG. 8; and

FIG. 10 is an enlarged sectional view taken along line 10-10 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,wherein like reference numerals will be used throughout the severalviews to identify like elements of the invention, there is disclosed inFIG. 1 a portion ofa snowmobile frame l on which is mounted a frontdrive sprocket wheel ll having a plurality of sprocket teeth l2, a rearidler sprocket wheel 13 having a plurality of sprocket teeth 14, and aplurality of spring-loaded bogie wheel assemblies 15, 16 and 17. Mountedbeneath and partially within the confines of frame is an endless drivetrack or belt 18. Drive track 18 is provided with a first series 19 anda second series 20 of sprocket engaging openings formed at spacedintervals. The first series 19 and the second series 20 are formed alongthe opposite edges of the drive track 18 and are parallel to each other.The individual openings in each of the two series 19 and 20 may bedesignated by the letters a, b,

c, etc.

Each of the belt openings is generally rectangular and the openings ineach series are spaced so that they mesh with the associated drivesprocket wheel and idler sprocket wheel. Although only one set ofsprocket wheels is shown in FIG. l, it is evident that another set wouldbe required if the type of belt shown in FIG. 2 is used. For the purposeof reinforcing the drive belt openings, I provide a plurality ofgrommetlike reinforcing and wear elements 21, one for each of theopenings. Each of the elements 21 comprises a tubular sleeve portion 21aof a shape and size to snugly fit one of the openings in the series 19or 20, an inner marginal flange 2lb that projects generally radiallyoutwardly from one end of the sleeve portion 21a and which engages theinner surface of the belt 18, and an outer marginalclamping flange 21Cwhich overlies the outer surface of the drive track 18 around thesprocket tooth engaging opening. A clamping washer 22 underlies theclamping flange 21e` and is anchored in clamping engagement with theouter belt surface by the clamping flange 21C. The full construction andoperation of these reinforcing and wear elements 2l are fully describedin my copending patent application entitled Snowmobile Track," Ser. No.767,641 that was filed Oct. l5, |968. Drive track I8 is preferably madefrom fabric reinforced rubber. The track I8 is molded or formed as asingle unit so that no seams are present. The bottom ground engagingsurface of drive track 18, as shown in FIG. 2, is also provided with atread pattern that both protects the wear elements 2l and providestraction for the vehicle. These treads include ridges 25 surround eachopening and ribs 26 extending laterally outwardly from the ridges 25toward opposite side edges of the drive track 18. Additional treadforming or traction elements may be utilized but since they are notimportant to the present invention, they are not identified.

As shown in FIG. 2, the openings in each of the series 19 and 20 areequally spaced from adjacent openings, and each opening in one series islocated directly across the belt from a corresponding opening in theother series. Thus, openings 19a and 19b lie directly across fromopenings 20a and 20h. Since the openings are spaced apart, a portion ofthe molded belt 18 extends between openings 19a and 19h, and anotherportion extends between openings 20a and 20h. These two belt portionsalso lie directly across from each other.

Referring now to FIG. 2, there is shown in dotted lines fiberglassstiffeners 30, 31, 33, etc., that extend transversely across the belt toslightly less than the full width thereof, between the inner and outersurfaces thereof. The construction of a single stiffener is shown inFIG. 3. Stiffener 30 is molded` extruded or otherwise formed from aplurality of parallel monofIlament fiberglass threads that are embeddedin a resin binder. An important feature of the stiffener 30 is that thefiberglass threads or fibers extend longitudinally from one end to theother and are thus unidirectional. In actual practice, the stiffener 30is approximately one-eighth inch thick and one-half inch wide.Stiffeners 30-33, etc. as shown in FIGS. 2, 3 and 4, are positionedperpendicular to the longitudinal axis of the belt 18. Stiffener 30extends across the belt between a pair of openings 19a and 19b, and acorresponding pair of openings 20a and 20b in the other series.Preferably, the stiffener 30 is positioned halfway between the twoadjacent openings on each side of the belt. Stiffener 30 impartstransverse rigidity to the belt but at the same time it is sufficientlyflexible to bend upon impact with a solid object. Further, stiffener 30has a memory such that it always returns to the normal flat position. i

As best shown in FIGS. 2, 5, succeeding stiffeners 3l, 32, 33, etc. aremounted in the belt so that a single stiffener is positioned betweeneach pair of adjoining openings 2l. All of the stiffeners areconstructed in the same manner as that previously described forstiffener 30, all lie in parallel to each other, and all are positionedat equally spaced intervals.

The fiberglass stiffeners 30-33, etc. are incorporated into the beltduring the belt molding or forming process. Preferably, the stiffeners30-33, etc. are premolded and are provided with rounded corners as shownin FIG. 3 so that flex ing of the belt will not tend to cause thecorners and edges thereof to cut the belt material. As best shown inFIG. 5, a portion of the belt extends over the stiffener and a portionextends under it. Therefore, the stiffener is actually an integral partof the belt and is protected by the belt from contact with the groundsurface or from contact with the sprocket wheel teeth. The stiffenerstend to hold the belt flat in a transverse direction but of course donot prevent flexing of the belt in a longitudinal direction as it passesover the sprocket wheels. The stiffeners add very little weight to thebelt and they are very easy to insert during manufacture of the beltitself. Since the stiffeners are inherently flexible, there is littletendency for them to break during usage of the belt and there are norivets or other connections to break. For these reasons, the presentinvention offers a great improvement in performance as compared to beltsusing prior art stiffening methods.

Referring now to FIGS. 6 and 7, there is disclosed another embodiment offiberglass stiffener for use as previously described. This type ofstiffener comprises a group of flat laminations cured together to form asolid mass. Each of the laminations comprises a large number of parallelmonofllament fiber glass threads embedded in an epoxy resin binder. InFIG. 6, the individual laminations of a stiffener 35 are identified bythe letters a, b, c, d, e and f. The number of laminations is notcritical however, in FIG. 6, six laminations, a-f, are shown. In FIG. 7a stiffener 36 having six layers or laminations, a-f, is shown with fivelayers of epoxy resin interposed therebetween. When the laminations arecured together, a solid mass is formed and the resulting stiffener isused in the same manner as that previously described for stiffeners30-33. The laminated structure gives greater rigidity than the singlemolded structure of stiffener 30, and also has a better memory. I

ln construction of the laminated stiffener 35 or 36, each lamination mayutilize parallel fiber glass threads that extend from one end to theother, if desired. On the other hand, a stronger structure will resultif the threads in one lamination are skewed with respect to the threadsin another adjoining lamination. For example, referring to FIG. 6, it isnoted that the threads in lamination 35a extend from one end to theother thereof and lie in parallel with the side edges thereof. Thethreads in lamination 35b, however, lie at almost a 45 angle withrespect to the side edges thereof. The threads of lamination 35e alsolie at an angle with respect to the edges but lie at right angles withrespect to the threads in lamination 35b. By constructing the stiffenerin this manner, as shown in both FIGS. 6 and 7, the strength andtoughness of the resulting stiffener is much greater'than would be thecase where all of the threads in the stiffener run inthe same direction.

Another approach to constructing the stiffener is shown in FIGS. 8, 9and 10. FIG. 8 disclosed a stiffener comprising a pair of flat fiberglass strips 37 and 38 secured together at their opposite ends andspaced apart intermediate their ends. Each of the strips 37 and 38 beconstructed as a single unit similar to stiffener 30 or may beconstructed as a laminated stiffener in the manner of stiffeners 35 and36. ln any event, however, the two strips 37 and 38 are secured togetherfor a short distance at their opposite ends but are bowed apartintermediate their ends as shown in the drawings. During construction ofthe belt 18, the belt material, normally rubber, is not only positionedon opposite sides of the strips 37 and 38 but is also placed betweenthem. When the rubber belt is vulcanized, the stiffener is embeddedwithin the belt as previously described, but with the rubber beltmaterial also extending between the two strips 37 and 38. A trussstructure is thus formed by the strips 37 and 38 that strongly resistsbending from its normal position, and that will quickly return to itsnormal position if it is flexed. Again, a plurality of these stiffeners,each comprising a pair of flat strips 37 and 38, will be molded into thebelt as shown and described previously with respect to stiffeners 30- 33etc. ln all cases, the outer edges and corners of the stiffeners arerounded off to avoid causing damage to the belt material during normalusage thereof.

The particular means of bonding the monofllament fiberglass threadstogether is not critical to my invention. Epoxy resin is normally usedbut other bonding materials could be used if they provided similarproperties. Further, the stiffeners are normally formed in advance ofthe belt forming operation so that the belt molding or vulcanizingoperation has no affect on the properties of the stiffeners. However, lalso intend to cover a stiffener of the type that would be placed in thebelt in an uncured condition, and thereafter cured at the same time thatthe belt material is cured. The resulting structure would be identical,but the method of constructing it would be slightly different.

Also, l have disclosed a belt having two series of sprocket wheel teethengaging openings. As shown in my copending application entitledSnowmobile Track," Ser. No. 767,641, however, it is common practice inthe snowmobile industry to utilize a belt having only a single row orseries of openings formed therein. ln that type oftrack, the series ol`openings lies along thc longitudinal center of the belt so as to engagea single drive sprocket wheel. Since that type of belt also requiresmeans of providing transverse rigidity, l intend that the samestiffeners be used in that type of belt. ln such case, the stiffenerswould again extend between the adjacent openings to basically the fullwidth of the belt. Actually, my invention is applicable to any type offlexible molded drive belt, regardless of how it is driven. My inventiveapproach to imparting transverse rigidity to a flexible drive belt isapplicable to a wide variety of belt constructions and is not limited toa belt having sprocket teeth engaging openings. Therefore, my inventionshould not be limited to the details disclosed in the specification anddrawings, but only by the scope of the appended claims.

What I claim is:

l. In an endless, flexible vehicle driven belt with an inner surface anda ground engaging outer surface, the improvement comprising means toimpart transverse rigidity to said belt, said means including aplurality of spaced, fiber glass stiffeners extending transversely ofsaid belt between the inner and outer surfaces thereof, said stiffenerseach comprising a plurality of parallel monofilament fiberglass threadsembedded in a resin binder.

2. ln a vehicle drive track comprising an endless'rubber belt with aninner surface, a ground engaging outer surface and a first and secondseries of longitudinally spaced openings therethrough for engagementwith the teeth of a pair of spaced drive sprocket wheels, theimprovement comprising means to impart transverse rigidity to said belt,said means including a plurality of flat, fiber glass stiffeners moldedinto said belt so as to be completely surrounded by said rubber belt,each of said stiffeners extending transversely of said belt between acorresponding pair of openings in each of said first and second series,to generally the full width of the belt.

3. In an endless, flexible vehicle driven belt with an inner surface anda ground engaging outer surface, the improvement comprising means toimpart transverse rigidity to said belt, said means including aplurality of spaced, fiberglass stiffeners extending transversely ofsaid belt between the inner and outer surfaces thereof, said stiffenerseach comprising a group of flat laminations cured together to form asolid mass, each of said laminations comprising a plurality of parallelmonolament fiberglass threads embedded in a resin binder.

4. The apparatus of claim 3 wherein said threads in one lamination areskewed with respect to the threads in an adjacent lamination.

5. ln an endless, flexible vehicle driven belt with an inner surface anda ground engaging outer surface, the improvement comprising means toimpart transverse rigidity to said belt, said means including aplurality of spaced, fiberglass stiffeners extending transversely ofsaid belt between the inner and outer surfaces thereof, said stiffenerseach being flat and having a generally rectangular cross section withthe corners and edges thereofbeing rounded off to reduce wear on theadjoining belt material.

6. ln an endless, flexible vehicle driven belt with an inner surface anda ground engaging outer surface, the improvement comprising means toimpart transverse rigidity to said belt, said means including aplurality of spaced, fiber glass stiffeners extending transversely ofsaid belt between the inner and outer surfaces thereof, said stiffenerseach comprising a pair of flat fiber glass strips secured together attheir opposite ends and spaced apart intermediate said ends, thematerial of said belt extending between said strips as well as over andunder said strips, whereby a truss structure is formed by each of saidstiffeners.

1. In an endless, flexible vehicle driven belt with an inner surface anda ground engaging outer surface, the improvement comprising means toimpart transverse rigidity to said belt, said means including aplurality of spaced, fiber glass stiffeners extending transversely ofsaid belt between the inner and outer surfaces thereof, said stiffenerseach comprising a plurality of parallel monofilament fiberglass threadsembedded in a resin binder.
 2. In a vehicle drive track comprising anendless rubber belt with an inner surface, a ground engaging outersurface and a first and second series of longitudinally spaced openingstherethrough for engagement with the teeth of a pair of spaced drivesprocket wheels, the improvement comprising means to impart transverserigidity to said belt, said means including a plurality of flat, fiberglass stiffeners molded into said belt so as to be completely surroundedby said rubber belt, each of said stiffeners extending transversely ofsaid belt between a corresponding pair of openings in each of said firstand second series, to generally the full width of the belt.
 3. In anendless, flexible vehicle driven belt with an inner surface and a groundengaging outer surface, the improvement comprising means to imparttransverse rigidity to said belt, said means including a plurality ofspaced, fiberglass stiffeners extending transversely of said beltbetween the inner and outer surfaces thereof, said stiffeners eachcomprising a group of flat laminations cured together to form a solidmass, each of said laminations comprising a plurality of parallelmonofilament fiberglass threads embedded in a resin binder.
 4. Theapparatus of claim 3 wherein said threads in one lamination are skewedwith respect to the threads in an adjacent lamination.
 5. In an endless,flexible vehicle driven belt with an inner surface and a ground engagingouter surface, the improvement comprising means to impart transverserigidity to said belt, said means including a plurality of spaced,fiberglass stiffeners extending transversely of said belt between theinner and outer surfaces thereof, said stiffeners each being flat andhaving a generally rectangular cross section with the corners and edgesthereof being rounded off to reduce wear on the adjoining belt material.6. In an endless, flexible vehicle driven belt with an inner surface anda ground engaging outer surface, the improvement comprising means toimpart transverse rigidity to said belt, said means including apluraLity of spaced, fiber glass stiffeners extending transversely ofsaid belt between the inner and outer surfaces thereof, said stiffenerseach comprising a pair of flat fiber glass strips secured together attheir opposite ends and spaced apart intermediate said ends, thematerial of said belt extending between said strips as well as over andunder said strips, whereby a truss structure is formed by each of saidstiffeners.